Protection of Steel Constructions

Protection of Steel Constructions


Due to its functionality and, durability, efficiency in application, and great choice of architectural solutions for design and planning of buildings, steel is among the widest used materials in modern construction industry. However, in case of fire, in very short time unprotected steel may reach critical temperature at which it loses stability and load-bearing capacity, which as a result may cause a building to collapse, and catastrophic social and economic consequences. Therefore it is logical that in the total consumption of intumescent coatings all over the world, around 80% goes to steel protection.

Building materials such as structural steel are classified according to their performance in a case of fire. Durability of a material in a fire condition is determined by testing expressed in minutes and divided into categories. For instance, depending on standards of a certain country, the testing is expressed in line with testing of fire protection time length: 30, 45, 60, 90 or more minutes.

Increase of temperature in time in test furnace

Test furnace

Steel profiles after furnace testing

Apart from a type of steel, crucial importance for classification of fire resistance lies in defining dimensions, geometry, and the number of exposed sides of a construction material to fire. This data is expressed by section factor fp=Fp/V (m-1) which describes the relation of effective perimeter of a profile exposed to fire (Fp) divided by the cross-sectional area (V).

Steel profiles with section factor fp = 300 m-1 (large perimeter and small cross-sectional area) have the low resistance to fire and, as a consequence, they need high level of fire protection, actually a thicker film of an intumescent coating, in order to meet required fire protection time (which is defined by official testing in accredited institutes).

Steel profiles with section fp = 160 m-1 (small perimeter and large cross-sectional area) on the other hand, have greater resistance to fire so they need lees protection, i.e. thinner film of an intumescent coating.

A


Steel profiles with lower values of section factor. Higher resistance to fire and necessary lower level of fire protection.

B


Steel profiles with higher values of section factor. Smaller fire resistance and higher level of fire protection is needed.

An unprotected steel bearer quickly reaches critical temperature in a fire situation which is about 500° C, after which a building or its part deform and finally collapse. Deformation of a steel bearer is a consequence of a sudden fall in hardness of steel which appears already at 200°C, while at 500°C it drops to half of its original value. Deformation of steel columns causes them to bend or even break, which causes the entire building to collapse. Depending on a type of a combustible material and ventilation conditions, fire may have different dynamics, thermic force, and strength, which all affect thermal load on building constructions.

View of protected support columns compared to unprotected and deformed parts of construction after fire

Display of ideally formed foam layer of intumescent coating

It is obvious that suitable fire protection of steel constructions in a certain length of time is important. Many systems such as vermiculite plaster, boards made of non-flammable materials, mineral wool, various perlite plasters, etc. proved to be additional load for support elements, more complicated to appl, and with less appealing esthetics. Therefore, the system based on intumescent coatings is the best choice in this area.

FIRESTOP systems based on coatings FIRESTOP steel X-MART 110 and FIRESTOP steel X-MART 111 are the ideal solution for efficient fire protection of steel constructions in the interior and exterior (semi-exposer). Combined with a suitable anti-corrosive primers and a top coats, these systems provides protection of steel from corrosion and atmospheric conditions, while giving it attractive appearance to the treated elements.